This invention relates to routing calls through a network.
Devices can communicate multimedia information such as sounds, video, data, and other types of similar information in real time over a network using a protocol such as Session Initiation Protocol (SIP) or H.323 (International Telecommunications Union (ITU) standard approved in 1996, H.323 version two approved in January 1998). The network may be a packet-based network, such as an Internet Protocol (IP) network. SIP and H.323 can each enable functions such as call routing, call signaling, capabilities exchange, media control, and other similar functions. SIP and H.323 are each described further below.
SIP is a signaling protocol that can facilitate initiation, maintenance, and termination of a communication session between SIP user agents, SIP software included in or accessible by a device. A SIP user agent (called a client when sending a request) can send a communication session request to another user agent (called a server when receiving and responding to a request) over an IP network. SIP can enable the client and the server to agree upon characteristics of the communication session, such as service policies, media types, etc.
H.323 defines a set of standards that may be used in communicating multimedia information between telephony and IP networks and enabling calls to be routed, controlled, and transported by an IP network. A client and a server may use H.323 standards in initiating, maintaining, and terminating a communication session.
Clients and servers with H.323 capability typically use four main components: terminals, gateways, gatekeepers, and multipoint control units (MCUs). Terminals generally include applications running at the endpoints of the communication session, e.g., at the client(s) and the server(s) involved in a communication session. Gateways generally include mechanisms that enable clients to communicate with non-H.323 devices by translating between different communication services, transmission policies, coding/decoding procedures, and other similar operations. Gatekeepers generally include mechanisms that provide network services such as bandwidth control, call control, address translation, and other similar services to terminals, gateways, and MCUs. MCUs generally include mechanisms that enable multiple terminals to participate in a single communication session.
Referring to FIG. 1, for example, a network configuration 100 illustrates a sample of a call setup from a terminal with an H.323 endpoint 108 to an H.323 gateway 110 included in an H.323 network 104. Thus, in this example, the terminal 108 represents the client and the gateway 110 represents the server. The call starts as the terminal with an H.323 endpoint 108 sends an address request directed to a gatekeeper 112 included in the H.323 network 104, seeking to find the IP address of H.323 gateway 110. The address request is transmitted over an IP network 114.
The ingress gatekeeper 112 communicates with a directory and egress gatekeeper 106 included in the H.323 network 104 using a protocol used to route calls to available resources through the IP network 114 such as registration, admission, and status (RAS).
The ingress gatekeeper 112 may send a location request to the egress gatekeeper 106. The egress gatekeeper 106 may respond with a location confirmation indicating the IP address of H.323 gateway 110. The ingress gatekeeper 112 may send an address confirmation to the terminal 108 that the terminal 108 may accept to begin communications with the gateway 110. The terminal 108 can communicate with the gateway 110 using a call control mechanism such as the H.245 standard (ITU H.245 standard recommended in February 2000) and a channel or packet transfer mechanism such as the H.225 standard (ITU H.225.0 standard recommended in November 2000). H.245 and H.225 are typically used for call control operations such as setup, teardown, redirection, and other similar operations. After any call control operations, the terminal 108 and the gateway 110 can communicate in a real-time transport protocol (RTP) or real-time transport control protocol (RTCP) communication session.
The client(s) and server(s) that desire to establish a communication session may not all be enabled with the same communication protocol.
FIG. 2 illustrates a sample of a call setup between a terminal 116 with a SIP user agent and the H.323 gateway 110 in H.323 network 104, that now includes Ingress SIP proxy 112 and a SIP to H.323 protocol converter 122 to provide SIP to H.323 protocol conversion. First, a SIP call is setup between the terminal with SIP user agent 116 and the SIP to H.323 protocol converter 122, and then an H.323 call is setup between the SIP to H.323 protocol converter 122 and the H.323 gateway 110.